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.\" Copyright (c) 2024 Florian Walpen <dev@submerge.ch>
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.Dd October 28, 2024
.Dt SND_HDSP 4
.Os
.Sh NAME
.Nm snd_hdsp
.Nd "RME HDSP bridge device driver"
.Sh SYNOPSIS
To compile this driver into the kernel, place the following lines in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device sound"
.Cd "device snd_hdsp"
.Ed
.Pp
Alternatively, to load the driver as a module at boot time, place the
following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
snd_hdsp_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
bridge driver allows the generic audio driver
.Xr sound 4
to attach to RME HDSP audio devices.
.Sh HARDWARE
The
.Nm
driver supports the following audio devices:
.Pp
.Bl -bullet -compact
.It
RME HDSP 9632 (optional AO4S-192 and AIS-192 extension boards)
.It
RME HDSP 9652
.El
.Pp
By default, each
.Xr pcm 4
device corresponds to a physical port on the sound card.
For ADAT ports, 8 channel, 4 channel and 2 channel formats are supported.
The effective number of ADAT channels is 8 channels at single speed
(32kHz-48kHz) and 4 channels at double speed (64kHz-96kHz).
Only the HDSP 9632 can operate at quad speed (128kHz-192kHz), ADAT is
disabled in this mode.
Depending on sample rate and channel format selected, not all pcm channels can
be mapped to ADAT channels and vice versa.
.Sh LOADER TUNABLES
These settings can be entered at the
.Xr loader 8
prompt or in
.Xr loader.conf 5 .
.Bl -tag -width indent
.It Va hw.hdsp.unified_pcm
If set to 1, all physical ports are combined into one unified pcm device.
When opened in multi-channel audio software, this makes all ports available
at the same time, and fully synchronized.
For resulting channel numbers consult the following table:
.El
.Bl -column "Sound Card" "Single Speed" "Double Speed" "Quad Speed"
.Sy "Sound Card" Ta Sy "Single Speed" Ta Sy "Double Speed" Ta Sy "Quad Speed"
.It "" Ta "Play | Rec" Ta "Play | Rec" Ta "Play | Rec"
.It HDSP 9632 Ta " 16  |  16" Ta " 12  |  12" Ta "  8  |   8"
.It HDSP 9652 Ta " 26  |  26" Ta " 14  |  14" Ta "  -  |   -"
.El
.Sh SYSCTL TUNABLES
These settings and informational values can be accessed at runtime with the
.Xr sysctl 8
command.
If multiple RME HDSP sound cards are installed, each device has a separate
configuration.
To adjust the following sysctl identifiers for a specific sound card, insert
the respective device number in place of
.Ql 0 .
.Bl -tag -width indent
.It Va dev.hdsp.0.sample_rate
Set a fixed sample rate from 32000, 44100, 48000, up to 192000.
This is usually required for digital connections (AES, S/PDIF, ADAT).
The default value of 0 adjusts the sample rate according to pcm device settings.
.It Va dev.hdsp.0.period
The number of samples processed per interrupt, from 32, 64, 128, up to 4096.
Setting a lower value here results in less latency, but increases system load
due to frequent interrupt processing.
Extreme values may cause audio gaps and glitches.
.It Va dev.hdsp.0.clock_list
Lists possible clock sources to sync with, depending on the hardware model.
This includes internal and external master clocks as well as incoming digital
audio signals like AES, S/PDIF and ADAT.
.It Va dev.hdsp.0.clock_preference
Select a preferred clock source from the clock list.
HDSP cards will sync to this clock source when available, but fall back to
auto-sync with any other digital clock signal they receive.
Set this to
.Ql internal
if the HDSP card should act as master clock.
.It Va dev.hdsp.0.clock_source
Shows the actual clock source in use (read only).
This differs from what is set as clock preference when in auto-sync mode.
.It Va dev.hdsp.0.sync_status
Display the current sync status of all external clock sources.
Status indications are
.Ql none
for no signal at all,
.Ql lock
for when a valid signal is present, and
.Ql sync
for accurately synchronized signals (required for recording digital
audio).
.El
.Pp
The following tunables are applicable to HDSP 9632 devices only:
.Bl -tag -width indent
.It Va dev.hdsp.0.input_level
Select the sensitivity of the analog line input.
Available reference levels for the input signal are
.Ql LowGain ,
.Ql +4dBu
and
.Ql -10dBV .
.It Va dev.hdsp.0.output_level
Select the gain level of the analog line output.
Available reference levels for the output signal are
.Ql HighGain ,
.Ql +4dBu
and
.Ql -10dBV .
.It Va dev.hdsp.0.phones_level
Adjust the gain level of the phones output, separately from the analog line
output.
The signal can be lowered by 6 or 12 dB.
.El
.Pp
Where appropriate these sysctl values are modeled after official RME software on
other platforms, and adopt their terminology.
Consult the RME user manuals for additional information.
.Sh SEE ALSO
.Xr sound 4
.Sh HISTORY
The
.Nm
device driver first appeared in
.Fx 15.0 .
.Sh AUTHORS
.An -nosplit
Based on
.Xr snd_hdspe 4
originally written by
.An Ruslan Bukin <br@bsdpad.com> .
All adaptation to HDSP cards by
.An Florian Walpen <dev@submerge.ch> .
